Antibacterial Compounds from Bacteria Isolated from Hot Springs Water in Saudi Arabia

Recently, the emergence of antimicrobial-resistant bacterial infections has been considered one of the global health crises that threaten communities. The rise and dissemination of resistance within bacterial pathogens make the effectiveness of antibiotics decline gradually over time. As a result, the search for novel antibiotics from different natural sources has increased. Some microorganisms are able to produce secondary metabolites for protection. Bacteria, for example, have the ability to yield antibiotics. One important habitat that has yet to be fully exploited for antibiotic-producing bacteria is geothermal springs. Hot springs have been used for spas as well as for treating dermatological infections. Thirty-two water samples were collected from six different hot springs in Saudi Arabia. Several biological and microbiological assays were used to assess the antibacterial activities of samples against antimicrobial-resistant- and susceptible-bacterial strains and identify the genus and species of antibiotic-producing bacteria. Moreover, chromatographic and spectroscopic techniques were utilized to isolate the active compounds, and aid structural elucidation. The cross-streak assay’s findings illustrated that there were 14 bacteria with antimicrobial activities against most of the resistant- and susceptible-bacterial strains. 16S rRNA gene sequencing demonstrated that all antibiotic-producing bacteria to be Bacillus species; Bacillus paralicheniformis (6), Bacillus licheniformis (2), Bacillus pumilus (5) and Bacillus cereus (1). Seven compounds were isolated from these bacteria: five of which were known and two compounds were novel. The outcomes of MIC assay showed that all isolated compounds had mild to moderate antibacterial activities (between 128 µg/mL and 512 µg/mL in compared to the control) against all tested strains except for one compound (cholesterol (OM2)), which had no activity. The other known compounds were phenylacetic acid (OM7), isovaleric acid (OM4), ethyl-4-ethoxybenzoate (OM5) and N-acetyltryptamine (OM1). The two new compounds were N1-(N,N-dimethylcarbamimidoyl)-N1-methylterephthalamide (OM3) that belongs to the guanidine class of antibiotics, which are commonly isolated from microbes and 3-methyl-2H,7H-pyrano[2,3-b]pyran-2,7-dione (OM6), coumarin-like structures, which are also known for their antibacterial activities. In summary, this is the first study to investigate antibiotic-producing bacteria from hot thermal springs in Saudi Arabia. Screening revealed the propensity to isolate Bacillus spp., which are known to produce antibiotics in other habitats, particularly soil and aquatic environments. New compounds of known antibacterial classes could be isolated illustrating the potential of hot thermal springs as a source of discovering antibiotics

PHYTOCHEMICAL FINGERPRINT AND BIOLOGICAL ACTIVITIES OF THREE MALAYSIAN FICUS DELTOIDEA CULTIVARS.

Background Ficus deltoidea (Moraceae), is a Malay Traditional Medicine locally known as Mas Cotek. Three varieties (angustifolia, deltoidea and kunslerii) has been indictincty used.  Aims We here aim to better understand their chemistry and bioactivities to inform future scientific and agronomic research. Methods We extracted and analyzed samples from these varieties by HPTLC and HPLC-UV. The in vitro screening looked up to the scavenging activities against both DPPH and NO radicals, inhibitory activity upon tyrosinase and cytotoxicity against human prostate cancer cells PC3, DU145 and LNCaP using the sulforhodamine B proliferation assay and the MTT mitochondrial viability assay. Results We achieved to analytically differentiate the three varieties  in term of the presence of flavonoids, establishing that vitexin, orientin and isoorientin may act as intraspecific and interorgan phytomarkers Their biological activities point out to the antioxidant value of extracts from the deltoidea and kunslerii varieties whilst the inhibition of tyrosinase is only present in the roots extract of the var. deltoidea which here we show is also endowed with cytotoxic activity against prostate cancer cells. Conclusion We suggest that the three Malaysian Ficus deltoidea botanical varieties (angustifolia, deltoidea and kunslerii) can be also considered chemovars. The least bioactive chemovar was angustifolia. The most active extract was from the roots of var. deltoidea that shows antioxidant, antimelanogenic and cytotoxic potential.  Keywords: Chemotaxonomy; Prostate Cancer; Tyrosinase; Antioxidant; Ficus